How do we know it was a challenge from the left?

I find this story about the primary challenge that may or may not be between Rep. Lloyd Doggett and State Rep. Joaquin Castro to be frustrating because it makes a huge assumption that it never bothers to verify.

Longtime Austin Congressman Lloyd Doggett might not face a primary election opponent anymore, but his short-lived contest against a young legislator exposed dissatisfaction among some of Doggett’s most dependable constituencies.

Some constituents believe that after 17 years in Washington, Doggett, 65, is less connected to the people back home and lukewarm in his support of some issues important to them, such as gay rights and immigration reform.

It doesn’t help that some people see Rep. Joaquin Castro, 37, as the future of the Democratic Party in Texas, where Hispanics drive much of the population growth.

Some of Doggett’s critics didn’t want to speak publicly against the congressman, but others were willing to discuss their politics on the record.

“I view him as being part of the status quo,” said Paul Saldaña, a Southeast Austin businessman and Democratic activist who, like some other Travis County Democrats, switched his support to Castro.

The article does go into the generational issues, which I have discussedbefore, and the Latino-versus-Anglo issues, but what it doesn’t address is whether Castro would have represented an upgrade on Doggett from a progressive perspective or not. Doggett has some critics who don’t think he’s done enough to push certain issues, and you can agree or disagree with them as you see fit. What goes completely undiscussed is whether Castro would be a more vocal and/or effective advocate for the causes those critics value. Phillip Martin tried to get a handle on the question a couple of months ago, but it’s not easily answered. Castro’s voting record in the Lege stands up pretty well, but as one of those critics said about Doggett, it’s about more than voting. I don’t think anyone really knows what they might have gotten with US Rep. Joaquin Castro, though at least now with the court-drawn map and the opening in CD20, we’ll soon be able to compare them directly.

All that said, the fact that there could have been and could still be this battle, and the possibility that Doggett could have been outflanked on his left, led to some positive outcomes:

A couple of months after Castro was introduced to the Austin political scene, Doggett declared his support for the repeal of the Defense of Marriage Act.

He was one of the last of 122 co-sponsors of the repeal when he signed on as a co-sponsor Oct. 3.

[…]

Glen Maxey, who was the first openly gay member of the Texas House, said he felt that Doggett’s opposition to the military’s “don’t ask, don’t tell” policy has been tepid over the years.

But Maxey said that the short-lived Doggett-Castro race resulted in both candidates taking encouraging positions on the repeal of the military’s ban on homosexuals.

“This campaign has made advocates out of two Democratic men,” Maxey said. “I’m pleased where the campaign ended.”